Method for producing a multilayer component

ABSTRACT

A method can be used for producing a fully active stack. A stack has the sides A, B, C and D running along the stacking direction. The method includes combining and temporarily making contact with the internal electrodes that make contact with the respective side on one of the sides B or D, such that the internal electrodes that make contact with the respective side can be electrically driven selectively. The electrically driven internal electrodes are electrochemically coated on the sides A and C. The stack is singulated to form a fully active stack with the electrochemically coated internal electrodes on the sides A′ and C′. A method for producing a multilayer component comprising the fully active stack and a fully active multilayer component producible according to the method are furthermore proposed.

This patent application is a national phase filing under section 371 ofPCT/EP2013/052214, filed Feb. 5, 2013, which claims the priority ofGerman patent application 10 2012 101 351.9, filed Feb. 20, 2012, eachof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to a fully active multilayer component, a methodfor producing a fully active stack, and a method for producing a fullyactive multilayer component comprising the fully active stack.

BACKGROUND

Multilayer components encompass capacitors and piezo-actuators,containing in each case alternating dielectric layers and internalelectrodes. In the case of the piezo-actuators, the dielectric layersare additionally piezoelectric. Therefore, piezo-actuators are includedamong the piezo-elements.

Piezo-elements are, inter alia, for positioning elements, ultrasonictransducers, sensors and in inkjet printers and also in automotiveengineering for driving fuel elements is based on the deformation ofpiezo-ceramic materials, such as e.g., lead zirconate titanate, underthe action of an electric field. If an electrical voltage is applied tothe piezo-element, then the latter expands in a direction perpendicularto the electric field generated (inverse piezo-effect).

Advantages of piezo-elements include, inter alia, the relatively highspeed thereof, the relatively high effectiveness thereof and, if used aspiezo-actuator, the relatively small actuating travel thereof.

However, if a relatively large actuating travel is intended to beachieved with the piezo-actuator, then a piezo-stack comprising aplurality of alternately successive piezo-electric layers and internalelectrode layers is used for the piezo-actuator, as is disclosed e.g.,in JP 03174783 A.

The piezo-actuator disclosed in JP 03174783 A is embodied in such a waythat the internal electrode layers are electrically connectedalternately to external electrodes arranged at opposite outer surfacesof the piezo-stack. The internal electrode layers, which areelectrically connected to one of the two external electrodes, aretherefore led as far as the outer side at which said external electrodeis arranged, for the electrical connection to the external electrode. Inorder that the internal electrode layers are electrically insulated fromthe other external electrode, however, the internal electrode layers donot extend as far as the outer side of the piezo-stack at which thefurther external electrode is arranged. In these regions, the internalelectrode layers are set back from the outer side. This is achieved bythe piezo-stack being provided with slots filled with silicone resin inthese regions.

By virtue of the set-back internal electrode layers, so-called inactivezones arise in piezo-electric layers assigned to these regions. Theinactive zones are usually produced during the layered production of thepiezo-stack. Owing to tolerances of the processes, stacking, separation,binder removal and grinding during the production of the piezo-stackwith inactive zones and on account of the stipulation of a reliableelectrical insulation of the internal electrode layers with respect tothe corresponding external electrode, relatively large inactive zones oftypically up to 10 percent of the piezo-stack cross section arise. Theinactive zones, which are permeated by a reduced electric field strengthwhen an electrical voltage is applied to the external electrode layersor internal electrode layers and therefore expand to a lesser extentthan the other, so-called active zones of the piezo-electric layers whenan electrical voltage is applied. This leads to mechanical stresses inparticular in the inactive zones and the edge regions with respect tothe inactive zones and can lead to so-called poling cracks in theinactive and active zones of the piezo-electric layers, and also in theexternal electrodes. The risk of poling cracks is all the higher, thelarger the inactive zones.

SUMMARY

Embodiments of the invention specify a multilayer component and a methodfor producing it in which the performance is improved in operation.Particular embodiments provide a piezo-actuator in which the mechanicalstresses in the piezo-ceramic are significantly reduced during theoperation of the piezo-actuator.

Embodiments of the invention can be achieved by use of a method forproducing a fully active stack or stacked bar or the green precursorthereof. A sintered or unsintered (initial) stack having the sides A, B,C and D running in each case in the stacking direction is provided. Thestack comprises a plurality of alternately successive ceramic dielectriclayers and internal electrode layers. The internal electrode layers areembodied in each case in a continuous fashion with respect to the sidesA and C and are embodied in each case in a non-continuous fashion withrespect to either the side B or the side D, such that one portion of theinternal electrodes or the unsintered precursors thereof make contactwith the side B, but not with the side D, and another portion of theinternal electrodes or the unsintered precursors thereof make contactwith the side D, but not with the side B. The method includes combiningand temporarily making contact with the internal electrodes that makecontact with the respective side or the unsintered precursors of saidinternal electrodes on one of the sides B or D via an external contactwith temporary isozones, such that the internal electrodes that makecontact with the respective side can be electrically driven selectively.The electrically driven internal electrodes or the unsintered precursorsthereof are electrochemically coated on the sides A and C. The stack issingulate to form a fully active stack or the green precursor thereofwith the electrochemically coated internal electrodes or the unsinteredprecursors thereof on the sides A′ and C′.

If a fully active piezo-stack is intended to be produced by the method,ceramic piezo-electric layers are used for the ceramic dielectriclayers. Preferably, the initial (stack) comprises regions in which theinternal electrode layers make contact with the sides A and Dalternately in each case. With particular preference, in the initial(stack) all the internal electrode layers make contact with the sides Aand D alternately in each case.

Further embodiments of the invention provide a method for producing afully active multilayer component comprising the fully active stackproduced according to the above method. In specific detail, for thispurpose, a fully active stack or the green precursor thereof is producedaccording to the above method and sintered, if appropriate. Afterward,external electrodes are applied on the sides A′ and C′ of the fullyactive stack and the electrochemically coated or uncoated internalelectrodes are contact-connected thereby, such that the two externalelectrodes are electrically connected either to the electrochemicallycoated or to the uncoated internal electrodes.

Yet other embodiments of the invention is achieved provide a fullyactive multilayer component comprising a fully active stack comprising aplurality of dielectric layers and internal electrode layers and twoexternal electrodes arranged on opposite sides of the stack. At leastone portion of the internal electrode layers are electrochemicallycoated. The two external electrodes are electrically connected in eachcase either to the electrochemically coated or to the electrochemicallyuncoated internal electrodes. The electrical connection of the twoexternal electrodes to a portion of the internal electrodes either isinterrupted by an oxide layer on the internal electrodes or is producedby an electrolytic coating of the internal electrodes. The fully activemultilayer component comprises a capacitor and a piezo-actuator. If afully active piezo-actuator is intended to be provided, the ceramicdielectric layers are ceramic piezo-electric layers.

In one particular embodiment according to the invention, the oxide layercontains a metal which differs from the metal contained in the internalelectrodes, preferably by being more electronegative than a metal usedin the internal electrodes. By way of example, the oxide layer cancomprise aluminum in the case of copper-containing internal electrodes.

In a further particular embodiment according to the invention, theelectrical connection of the external electrodes to a portion of theinternal electrodes is produced by means of an electrolytic coating ofthe internal electrodes and the electrical connection of the externalelectrodes to the rest of the internal electrodes is interrupted by anarrow isozone composed of ceramic having a width of 50 to 200 μm,preferably 50 to 100 μm.

According to the invention, a fully active stack should be understood tomean a stack in which the internal electrodes are continuous, i.e.,extend over the entire cross-sectional area of the stack. As a result ofthis configuration, the entire internal electrodes extend as far as theouter side of the stack, for which reason the latter has no inactivezones. As a result, the performance of the multilayer component duringoperation is improved and, in the case of the piezo-actuator, themagnitude of the mechanical stresses in the piezo-ceramic is reducedduring operation.

The (initial) stack provided in the method for producing a fully activestack is produced, for example, by at least two partial stacks beingstacked alternately, wherein each of the partial stacks has a dielectriclayer and an internal electrode layer arranged thereon. In this case,the stack provided is produced, in particular, by so-called greenceramic sheets being printed with metallic pastes, for example, usingthe screen printing method. In this case, the printing is performed insuch a way that the metallic pastes completely cover the ceramic greensheet, wherein an unprinted edge is left on one side. The metallicpastes comprise e.g., AgPd or Cu particles, solvents and furtheradditives. Afterward, typically approximately 300 to 600 green ceramicsheets provided with the paste from the two partial stacks are placedone above another in such a way that a block arises in which themetallic intermediate layers make contact with two opposite sidesalternately and every second intermediate layer is oriented identicallywith respect to the unprinted edge. The stack produced is then processedby pressing to form a so-called green block. Afterward, the green blockis subjected to binder removal in order to remove solvent residues andis sintered, if appropriate. From a green block, if appropriate, aplurality of (initial) stacks or stacked bars can be produced by meansof separation into individual stacks.

In the method for producing a fully active stack or the green precursorthereof, the (initial) stack provided in the first step can be eithersintered or green. If the stack is sintered, this has the advantage thatthe risk of impairment of the ceramic intermediate layers in thepiezo-stack during the implementation of the electrochemical coating islow.

In one embodiment according to the invention, the process ofelectrochemically coating the electrically driven internal electrodes onthe sides A and C is carried out by means of electrochemical oxidation,preferably by anodic oxidation. According to the invention, anodicoxidation is understood to mean an electrolytic method for producingoxidic layers on metals. Alternatively, the process of electrochemicalcoating can be effected by means of plating technology orelectroplating. According to the invention, plating technology orelectroplating is understood to mean the electrochemical deposition ofmetallic layers on articles.

In one particular embodiment according to the invention, before theprocess of electrochemical coating all the internal electrodes areetched back, preferably according to the principle of electrochemicalmachining. According to the invention, electrochemical machining isunderstood to mean a method for removing metal by an electrochemicalmethod.

In one particular embodiment according to the invention, after theprocess of electrochemical coating by means of plating technology theuncoated internal electrodes are covered with insulating material. Ifetching back was effected before the process of electrochemical coatingby means of plating technology, the process of electrochemical coatingby means of plating technology is preferably carried out beyond theetching depth.

In one particular embodiment according to the invention, after theprocess of electrochemical coating by means of plating technology thecoating is converted into an insulating oxide coating by electrochemicaloxidation, preferably by anodic oxidation. For this purpose, anelectrolytic coating material that differs from the material of theinternal electrode is preferably used. Preferably, the electrolyticcoating material is more readily oxidizable than the material of theinternal electrode. By way of example, a metal or a metal mixturecontaining aluminum can be used if the internal electrodes comprisecopper.

In one particular embodiment according to the invention, the trenchesthat are not filled again after the etching-back process are closed bysintering. In this case, a green piezo-stack is preferably taken as astarting point in the method for producing a fully active piezo-stack.In this way, a particularly economic method is possible since anadditional insulating material or method steps for applying the lattercan be dispensed with. Moreover, particularly narrow inactive zones orisozones having a width of 50 to 200 μm, preferably 50 to 100 μm, can beproduced in this way.

In one particular embodiment according to the invention, theelectrochemical coating is carried out in an aqueous NaCl solution aselectrolyte. An AC voltage, e.g., 50 HZ, can be used in this case. Forthis purpose, the internal electrodes preferably consist of silver or asilver alloy, with further preference AgPd. In this way, a silver oxidelayer grows on the voltage-carrying electrodes (see, e.g., BAEWA, W.“Oxidation von Silber durch Wechselstrom von 50 HZ in wässrigerNatriumlösung” [“Oxidation of silver by AC current at 50 Hz in aqueoussodium solution”] in Werkstoffe and Korrosion, volume 22, edition 2,page 143 et seq., issue February 1971).

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated by way of examplein the accompanying schematic drawings, in which:

FIG. 1 shows a perspective side view of a piezo-stack having the sidesA, B, C and D along the stacking direction;

FIG. 2 shows an electrolysis bath for electrochemically coating apiezo-stack;

FIGS. 3A and 3B show the oxide layers applied on the internalelectrodes;

FIG. 4 shows a singulated fully active piezo-stack having the sides A′,B′, C′ and D′ along the stacking direction;

FIG. 5A shows a piezo-stack with applied electrolytic coating over theelectrically driven internal electrodes;

FIG. 5B shows a piezo-stack with additionally applied insulationmaterial;

FIG. 5C shows the piezo-stack after a further polishing step, such thatthe electrolytic coating is exposed;

FIG. 6A shows a piezo-stack with internal electrodes etched back to formtrenches;

FIG. 6B shows a piezo-stack with trenches partly filled again byelectrolytic coating;

FIG. 6C shows the piezo-stack additionally coated with insulationmaterial with the remaining trenches being filled;

FIG. 6D shows the piezo-stack after an additional polishing step; and

FIG. 6E shows the fully active piezo-stack finally provided with anexternal electrode.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In a first exemplary embodiment, the process sequence is as follows.

a) A sintered piezo-stack (1) having the sides A, B, C and D along thestacking direction is provided. The piezo-stack has (temporary) isozonesand external contact-connections (3), such that every second internalelectrode (2) on the side B can be electrically driven via the externalcontact-connection (3) and every second internal electrode (2′) can beelectrically driven via the corresponding external contact-connection(3′, not shown), on the side D (see, e.g., FIG. 1).

b) The piezo-stack (1) is dipped on one side (side C) into anelectrolyte solution (6) (FIG. 2), (positive) voltage is applied to thepiezo-stack (1) at the external contact-connection (3) of the side B,negative voltage is applied to the counterelectrode (5), andenergization takes place for a few minutes. An oxide layer (4) forms atthe voltage-carrying internal electrodes (2) of the piezo-stack (1)(see, e.g., FIG. 2, FIG. 3A and FIG. 3B). The principle of anodicoxidation is used in this case.

c) Method step b) is carried out analogously for the side A of thepiezo-stack (1).

d) The piezo-stack (1) with the coated internal electrodes (2, 2′) issingulated to form fully active piezo-stacks (12) (FIG. 4).

e) External electrodes (11) are applied on the sides A′ and C′ bymetallization with conductive adhesive or metallization paste, saidexternal electrodes, in each case on the corresponding side, makingelectrical contact with the internal electrodes not provided with anoxide layer, i.e., internal electrodes (2′) on side A′ and respectivelyinternal electrode (2) on side C′.

Steps d) and e) can also be processed in the reverse order.

In one variant of the first exemplary embodiment, an aqueous NaClsolution is used as electrolyte and an electrical AC voltage is appliedbetween the piezo-stack (1) via the internal electrodes (2) driven bythe external contact-connection (3) and the counterelectrode (5). Inthis variant, the internal electrodes consist of silver or a silveralloy, e.g. AgPd, as a result of which a silver oxide layer grows on thevoltage-carrying electrodes (see, e.g., BAEWA, W. “Oxidation von Silberdurch Wechselstrom von 50 HZ in wässriger Natriumchloridlösung”[“Oxidation of silver by AC current at 50 HZ in aqueous sodium chloridesolution”] in Werkstoffe and Korrosion, volume 22, edition 2, page 143et seq., issue February 1971).

In a further variant of the first exemplary embodiment, the internalelectrodes (2, 2′) to be coated are firstly removed 1 to 10 μm,preferably 1 to 5 μm, into the depth by the principle of electrochemicalmachining, as a result of which electrochemically etched-back trenches(9) arise. Afterward, the process of anodic oxidation is carried out, ifappropriate by changing the electrolyte. As a result, an oxide layer isobtained which extends further into the component depth and thus ensuresbetter insulation.

In a second exemplary embodiment, the process is carried out as follows.

a) A sintered piezo-stack (1) having lateral (temporary) isozones andexternal contact-connections (3) is provided (FIG. 1).

b) The side C of the component is dipped into a plating technologycoating basin, and negative potential is applied to the internalelectrodes (2) via the external contact-connection (3) on the side B ofthe piezo-stack (1). A metal layer several μm thick (typically 10 to 20μm) is deposited (process of plating technology) at the nowvoltage-carrying internal electrodes (2) (cathodes).

c) Method step b) is now repeated analogously for the side A.

d) The structured surface of the piezo-stack (1) (see, e.g., FIG. 5A) isnow smoothed with insulation material (8) (see, e.g., FIG. 5B). Glass ororganic lacquer is preferably used as insulation material.

e) The surfaces A and C of the bar are polished, such that the platedoutwardly situated electrodes (7) are sufficiently free and suitable fora further metallization (e.g., spattering, regrinding, etc.). The moredeeply situated electrodes still remain insulated from the surface as aresult of this cleaning step.

f) An external metallization is now applied on sides A and C and thepiezo-stack is singulated to form fully active piezo-stacks andprocessed further.

In a third exemplary embodiment, the process sequence is as follows(see, e.g., FIGS. 6A to 6E).

a) A sintered piezo-stack (1) having lateral (temporary) isozones andexternal contact-connections (3) is provided (FIG. 1).

b) The piezo-stack (1) is dipped on one side (side C) into a suitableelectrolyte solution (FIG. 2), (positive) voltage is applied to thepiezo-stack (1) at the internal electrodes (2) via the externalcontact-connection (3) on the side B and, at the same time, to theinternal electrodes (2′) via the external electrode (3′) (not shown) onthe side D, negative voltage is applied to the counterelectrode (5), andenergization takes place for a few minutes. All the electrodes arethereby etched back by 1 to 10 μm, preferably 1 to 5 μm, by means of theprinciple of electrochemical machining.

c) Afterward, the side C of the piezo-stack (1) is dipped into a platingtechnology coating basin and negative potential is applied to theinternal electrodes (2) via the external contact-connection (3) on theside B of the piezo-stack (1). At the now voltage-carrying internalelectrodes (2) (cathodes), the etched trenches (9) are filled again withconductive material.

d) Method steps b) and c) are now repeated analogously for the side A.

e) The trenches (9) are now filled with insulating material (e.g.,glazed, or sealed with organic lacquer).

f) The surfaces A and C of the piezo-stack (1) are cleaned in such a waythat surfaces of the outwardly situated electrodes are sufficiently freeand suitable for a further metallization (e.g., sputtering, regrinding,etc.). The more deeply situated electrodes still remain insulated fromthe surface as a result of this cleaning step.

g) An external metallization is now applied on the sides A and C, andthe piezo-stack (1) is singulated to form fully active piezo-stacks (12)and processed further.

In a fourth exemplary embodiment, the process sequence is as follows.

a) A sintered piezo-stack (1) having lateral (temporary) isozones andexternal contact-connections (3) is provided (FIG. 1).

b) The piezo-stack (1) is dipped by the side C into an electrolysis bathand voltage is applied to the internal electrodes (2) via the externalcontact-connection (3) on the side B, and etching back 1 to 10 μm,preferably 1 to 5 μm, is effected according to the principle ofelectrochemical etching-back.

c) Afterward, the side C of the component is dipped into a platingtechnology coating basin, and negative voltage is applied to theinternal electrodes (2) via the external contact-connection (3) on theside B of the piezo-stack (1). A metal layer several μm thick isdeposited (process of plating technology), preferably beyond the etchingchannel, at the now voltage-carrying internal electrodes (2) (cathodes).A material that differs from the material of the internal electrode (2)is preferably used here. With further preference, a metal or a metalmixture that is more electronegative than the metal of the internalelectrode is used. By way of example, aluminum can be used.

d) Afterward, the electrolytic coating on the side C is oxidized byanodic oxidation.

Particularly effective insulation can be produced in this way.

e) Steps b) to d) are repeated analogously for the side A of the bar.

f) The component is singulated.

g) An external metallization is now applied on the sides A and C.

Steps f) and g) can also be carried out in the reverse order.

In a fifth exemplary embodiment, the process sequence is as follows.

a) A sintered piezo-stack (1) having lateral (temporary) isozones andexternal contact-connections (3) is provided (FIG. 1).

b) The side C of the piezo-stack (1) is dipped into a plating technologycoating basin and negative potential is applied to the internalelectrodes (2) via the external contact-connection (3) on the side B ofthe piezo-stack (1). A metal layer several μm thick (typically 10 to 20μm) is deposited (process of plating technology) at the nowvoltage-carrying internal electrodes (2) (cathodes).

c) Afterward, the electrolytic coating is converted into an oxidecoating by anodic oxidation.

d) Method steps b) and c) are now repeated analogously for the side A.

e) The component is singulated (FIG. 4).

f) An external metallization is applied on the sides A and C.

Steps e) and f) can also be processed in the reverse order.

In a sixth exemplary embodiment, the process sequence is as follows.

a) A green piezo-stack (1) having lateral (temporary) isozones andexternal contact-connections (3) is provided (FIG. 1).

b) The piezo-stack (1) is dipped on one side (side C) into a suitableelectrolyte solution, and (positive) voltage is applied to the internalelectrodes (2) via the external contact-connection (3) on the sides Band D and positive voltage is applied to the counterelectrode, andenergization takes place for a few minutes. As a result, all theinternal electrodes (2, 2′) are etched back according to the principleof electrochemical machining.

c) Afterward, the side C of the component is dipped into a platingtechnology coating basin, and positive potential is applied to theinternal electrodes (2) via the external contact-connection (3) of thepiezo-stack (1). At the now voltage-carrying internal electrodes (2)(anodes), the etched trenches (9) are filled again with conductivematerial.

d) Method steps b) and c) are now repeated analogously for the side A.

e) The green piezo-stack (1) is sintered, the non-filled trenches (9)being closed by sintering.

f) The surfaces A and C of the piezo-stack (1) are cleaned, such thatthe surfaces of the plated internal electrodes (2) are sufficiently freeand suitable for a further metallization (e.g., sputtering, regrinding,etc.). The more deeply situated internal electrodes (2′) still remaininsulated from the surface as a result of this cleaning step.

g) An external metallization is now applied on the sides A and C, andthe sintered piezo-stack (1) is singulated to form fully activepiezo-stacks (12) and processed further.

The invention claimed is:
 1. A method for producing a fully active stackor a green precursor of the fully active stack, the method comprising:providing a sintered or unsintered stack having sides A, B, C and Drunning in each case in a stacking direction, the stack comprising aplurality of alternately successive ceramic dielectric layers andinternal electrode layers, wherein the internal electrode layers areinternal electrodes and are embodied in each case in a continuousfashion with respect to the sides A and C and are embodied in each casein a non-continuous fashion with respect to either the side B or theside D, such that one portion of the internal electrodes makes contactwith the side B, but not with the side D, and another portion of theinternal electrodes makes contact with the side D, but not with the sideB; combining and temporarily contacting the internal electrodes thatmake contact with one of the side B or the side D via an externalcontact with temporary isozones, such that the internal electrodes thatmake contact with the side B or the side D are selectively electricallydrivable; etching back at least one portion of the internal electrodesthat make contact with the side B or the side D before electrochemicallycoating; electrochemically coating the internal electrodes that makecontact with the side B or the side D on the sides A and C beyond anetching depth, wherein the electrochemically coating is effected by aplating technology; converting the electrochemical coating into aninsulating oxide coating by electrochemical oxidation; and singulatingthe stack to form the fully active stack or the green precursor of thefully active stack with the coated internal electrodes on sides A′ andC′, wherein the sides A′ and C′ correspond to the sides A and C,respectively, after the stack is singulated.
 2. The method accordingclaim 1, wherein the etching back comprises electrochemical machining.3. The method according to claim 1, further comprising, after theelectrochemical coating, covering uncoated internal electrodes with aninsulating material.
 4. The method according to claim 1, wherein a metalor a metal mixture that differs from metal of the internal electrode isused as an electrolytic coating material.
 5. The method according toclaim 1, wherein trenches that are not filled again after theetching-back are closed by sintering.
 6. The method according to claim1, wherein the electrochemical coating is carried out in an aqueous NaClsolution as electrolyte.
 7. The method according to claim 1, wherein theinternal electrode layers comprise silver, a silver alloy, or copper. 8.The method according to claim 1, further comprising applying externalelectrodes on the sides A′ and C′ of the fully active stack andcontacting the electrochemically coated or uncoated internal electrodes,such that the external electrodes are electrically connected either tothe electrochemically coated or to electrochemically uncoated internalelectrode layers.
 9. The method according to claim 8, further comprisingsintering the fully active stack or the green precursor.
 10. A methodfor producing a fully active stack or a green precursor of the fullyactive stack, the method comprising: providing a sintered or unsinteredstack having sides A, B, C and D running in each case in a stackingdirection, the stack comprising a plurality of alternately successiveceramic dielectric layers and internal electrode layers, wherein theinternal electrode layers are internal electrodes and are embodied ineach case in a continuous fashion with respect to the sides A and C andare embodied in each case in a non-continuous fashion with respect toeither the side B or the side D, such that one portion of the internalelectrodes makes contact with the side B, but not with the side D, andanother portion of the internal electrodes makes contact with the sideD, but not with the side B; combining and temporarily contacting theinternal electrodes that make contact with one of the side B or the sideD via an external contact with temporary isozones, such that theinternal electrodes that make contact with the side B or the side D areselectively electrically drivable; etching back at least one portion ofthe internal electrodes that make contact with the side B or the side Dbefore electrochemically coating; electrochemically coating the internalelectrodes that make contact with the side B or the side D on the sidesA and C, wherein the electrochemically coating is effected by a platingtechnology; converting the electrochemical coating into an insulatingoxide coating by electrochemical oxidation; and singulating the stack toform the fully active stack or the green precursor of the fully activestack with the coated internal electrodes on sides A′ and C′, whereinthe sides A′ and C′ correspond to the sides A and C, respectively, afterthe stack is singulated.
 11. The method according claim 10, whereinetching back comprises electrochemical machining.
 12. The methodaccording to claim 10, further comprising, after the electrochemicallycoating, covering uncoated internal electrodes with an insulatingmaterial.
 13. The method according to claim 10, wherein a metal or ametal mixture that differs from the metal of the internal electrode isused as an electrolytic coating material.
 14. The method according toclaim 10, wherein trenches that are not filled again after theetching-back are closed by sintering.
 15. The method according to claim10, wherein the electrochemical coating is carried out in an aqueousNaCl solution as electrolyte.
 16. The method according to claim 10,wherein the internal electrode layers comprise silver.
 17. The methodaccording to claim 10, wherein the internal electrode layers comprise asilver alloy.
 18. The method according to claim 10, wherein the internalelectrode layers comprise copper.
 19. The method according to claim 10,further comprising applying external electrodes on the sides A′ and C′of the fully active stack by contacting uncoated internal electrodes,such that the external electrodes are electrically connected to theuncoated internal electrodes.
 20. The method according to claim 19,further comprising sintering the fully active stack or the greenprecursor.